Chair tilting mechanism



1 Feb. 20, 1968 R. DUFTON v 3,369,840

CHAIR TILTING MECHANISM Filed July 22, 1966 2 Sheets-Sheet 1 y 764 55 40 M a /5@ I nvenlor Ronald Dufton MISEGADES 8c DOUGLAS Attorney United States Patent 3,369,840 CHAIR TILTING MECHANISM Ronald Dufton, Bushey Heath, England, assignor to Dare-Inglis Products Limited, Harrow, Middlesex, England, a British company Filed July 22, 1966, Ser. No. 567,209 Claims priority, application Great Britain, July 23, 1965, 31,603/ 65 7 Claims. (Cl. 297-303) ABSTRACT OF THE DISCLOSURE A chair tilting mechanism comprising a base portion, a seat portion, a back-rest portion pivotally connected to the base portion, an elongated leaf spring mounted transversely of the pivot axis between the base and back-rest portions to resist pivotal movement therebetween; a tension adjustment device connecting the forward end of the leaf spring to the base portion, the rearward end of the leaf spring engaging the back-rest portion; an abutment pivotally mounted on the base portion engaging the leaf spring substantially at the center thereof to effect bowing of the leaf spring.

This invention concerns a chair tilting mechanism.

The principal object of the invention is the provision of an improved chair tilting mechanism which is robust and occupies less vertical space and may thus be housed conveniently beneath the seat portion of the chair.

Such chair tilting mechanisms have theretofore comprised structures employing a leaf spring having a free end and about whose other end the spring bends to provide the necessary resilience for the structure.

The improved chair tilting mechanism of the present invention differs in structure and action from such leaf spring structures as have heretofore been known in that the resiliency of the mechanism is produced by bowing the leaf spring at its center. Thus either end of the spring is completely free and so there is less tendency for the spring to fracture and the mechanism occupies less vertical space.

According to the present invention there is provided a chair tilting mechanism comprising a base portion, a seat portion, a back-rest portion, means connected to the backrest portion, means pivotally connecting the back-rest portion to the base portion, an elongated leaf spring mounted transversely of the pivot axis between the base and backrest portions and adapted to resist pivotal movement therebetween, a tension adjustment device for varying the residual tension in the spring, the forward end of the leaf spring being connected to the base portion by way of the tension adjustment device, the rearward end of the leaf spring engaging the means connected to the back-rest portion, and an abutment pivotally mounted on the base portion which engage the leaf spring substantially at the center thereof to effect bowing of the leaf spring.

The seat portion and back-rest portion may be pivotally connected as a unit to the base portion.

Alternatively the seat and back-rest portions may be pivotally connected to the base portion in such a way as to permit the back-rest portion to be pivoted with respect to the base portion to a greater extent than the seat portion. Thus the locus of movement of the back-rest portion may have a smaller radius than that of the locus of movement of the seat portion.

The base portion may comprise a cradle which is rotatably mounted on a pillar. The back-rest portion is preferably pivotally connected to the cradle about an axis disposed to the rear of the pillar.

The seat portion may be pivotally connected to the "ice cradle forwardly of the pillar and is connected by linkage means to the back-rest portion.

The invention is illustrated; namely by way of example, in the accompanying drawings, in which:

FIGURE 1 is a part-sectional elevation of a chair according to the present invention,

FIGURE 2 is a part-sectional elevation of part of the chair shown in FIGURE 1,

FIGURE 3 is a part-sectional elevation of a modified form of chair according to the present invention,

FIGURE 4 is a view similar to FIGURE 3 with the components in a different relative position, and

FIGURE 5 is a part cut-away perspective view of part of the chair shown in FIGURES 3 and 4.

In FIGURE 1 there is shown an ofiice chair comprising a seat portion 11 and a back-seat portion 12 attached to the seat portion 11. The seat portion 11 is provided, on its underside and somewhat to the rear of the centre thereof, with brackets 13. The brackets 13 are pivoted by a common pivot 14 to a cradle 15 which is rotatably mounted on the central stem 16 of a pillar type base for the chair, the cradle 15 and stem 16 forming the base portion of a tilting mechanism permitting tilting of the back-rest 12. As will be seen, the pivot 14 is disposed somewhat to the rear of the stem 16. Attached to an extension arm 17 of the cradle is a tension adjustment device 18, shown in more detail in FIGURE 2, which cooperates with the forward end 19 of a laminated leaf spring 20. The leaf spring 20 is elongate, the forward end 19 of the leaf spring 20 being adjacent a pivot pin 21 at the extreme forward end of cradle 15, while the rearward end 22 of the leaf spring 20 engages a pivot pin 23 adjacent the rear of the seat portion 11. The leaf spring 20 is thus mounted transversely of the pivot 14 which forms the pivot axis between the back-rest portion 12 and the cradle 15. The pivot pin 23 is attached to bosses 24 on the underside of the seat portion 11 adjacent its rear end.

An abutment 25, which is pivoted to the cradle 15 on a pivot 26, bears against the underside of the leaf spring 20 adjacent its centre between the ends 19, 22 to elfect bowing of the leaf spring 20.

It will be appreciated that, when not in use, the leaf spring 20 will be almost linear with the seat portion 11 positioned substantially horizontally. In use, however, the

seat portion 11 and back-rest portion 12 will tilt rearwardly about the pivot 14 to the position shown, for example, in FIGURE 1, and will effect flexing of the leaf spring 20 by engagement between the pivot 23 and the rearward end 22 of the leaf spring 20. The leaf spring 20 will bow in the manner shown, since it is effectively fixed with respect to the cradle 15, due to tension adjustment device 18 or, if device 18 is slack, due to pivot pin 21, and the abutment 25 will resist movement of the leaf spring 20, but will permit bowing thereof, such that the tensioning of the leaf spring 20 will resist the tilting action of the chair. It will be appreciated that the back-rest portion 12 will tilt with the seat portion 11 and to the same extent.

Referring now to FIGURE 2., the tension adjustment device 18 is shown in more detail. It will be seen that the forward end 19 of the leaf spring 20 is provided with a central aperture 27 within which there is disposed a screwthreaded bolt 28, the head 29 of which is too large to pass through the aperture 27 and thus rests on the upper surface of the leaf spring 20. The screw threaded bolt 28 passes through an aperture 30 in the arm 17 and is provided on the underside of the arm 17 with a nut 31 having an axial projection 32 which engages the undersurface of the arm 17, so that rotation of the nut 31 adjusts the position of the head 29 of the bolt 28. Thus by rotating the nut 31, the head 29 of the bolt 28 can be moved vertically so as to draw the end 19 of the leaf spring 20 into the broken-line position indicated at 19' to thereby pre-tension the leaf spring 20 so that it provides greater resistance to tilting action of the chair. Thus the tension in the leaf spring 20 can be adjusted to suit the weight of the person using the chair. When the tension adjustment device 18 is very slack, the pivot pin 21 provides the restraining force on the upper side of the end 19 of the leaf spring 20 during tilting of the chair. At other times, the head 29 provides the restraining force.

Referring now to the embodiment shown in FIGURES 3 to 5, there is shown a somewhat modified and preferred form of chair which provides a tilting action similar to that provided by the arrangement of FIGURE 1, but also provides for relative movement between the back-rest and seat portions. In view of the similarity between the construction of FIGURES 3 to and that of FIGURES 1 and 2, similar components have been allocated similar reference numerals with the addition of the reference letter a.

Referring to FIGURES 3 to 5, it will be seen that seat portion 11a is pivoted to cradle a at 21a and not at 14a, and thus is pivoted thereto forwardly of the stem 16. Back-rest 12a is connected at 34- to two integral arms 35, 36 which are disposed on opposite sides of cradle 15a and are pivoted thereto by the pivot 14a. Arms 35, 36 are pivoted intermediate the ends thereof to links 40, 41 respectively which in turn are pivoted to the seat portion 11a at opposite ends of the pivot 23a. Thus the rearward end of the leaf spring a controls the position of the back-rest portion 12a by engaging the pivot 23a which is connected to the back-rest portion 12a by the links 40, 41 and the arms 35, 36.

It will be appreciated that the back-rest portion 12a is adapted to pivot about pivot 14a and, as clearly indicated in FIGURE 3, the are x which defines the locus of movement of the back-rest portion 12a has a smaller radius than the arc y which defines the locus of the movement of the seat portion 11a. Thus, upon pivotal movement of seat portion 11a from the position indicated in FIGURE 3, to the position indicated in FIGURE 4, a pivotal movement of the seat portion 11a through an angle a will result in pivotal movement of the back-rest 12a through an angle a-i-B, where ,8 is the angle between the seat portion 11a and the arms 35, 36.

The use of an elongate resilient leaf spring 20 in the tilting mechanism allows the latter to be made very compact so as to save height.

Although shown as a multi-leaf spring, the leaf spring 20 can, of course, be a single leaf. It will be appreciated that, in the embodiments of both FIGURES l and 2 and FIGURES 3 to 5, the forward end 19 of the leaf spring will be acted upon by the pivot pin 21 (or 21a) when the tension adjustment device 18, 18a is slackened off, but, whether the pivot pin 21, 21a or tension adjustment device 18, 18a acts on the end 19 of the spring, the end 19 of the spring can still be considered as being fixed relative to the cradle 15 of the base portion of the seat.

In the particular embodiments described above, the seat portion 11, or 11a and the back-rest portion 12 or 12a are upholstered. It will, however, be appreciated that the terms seat portion and back-rest portion can refer, and are intended to include within their scope, the frames only for the seat and back-rest, i.e. as shown in FIGURE 4. The frame for the seat portion, moreover, may be removable without such removal affecting the operating of the tilting mechanism.

I claim:

1. A chair tilting mechanism comprising a base portion, a seat portion, a back-rest portion, means connected to the back-rest portion, means pivotally connecting the back-rest portion to the base portion, an elongated leaf spring mounted transversely of the pivot axis between the base and back-rest portions and adapted to resist pivotal movement therebetween, a tension adjustment device for varying the residual tension in the spring, the forward end of the leaf spring being connected to the base portion by way of the tension adjustment device, the rearward end of the leaf spring engaging the means connected to the back-rest portion, and an abutment pivotally mounted on the base portion which engages the leaf spring substantially at the center thereof to effect bowing of the leaf spring.

2. A mechanism as claimed in claim 1 in which the seat portion and back-rest portion are pivotally connected as a unit to the base portion.

3. A mechanism as claimed in claim 1 in which the seat and back-rest portions are both pivotally connected to the base portion to permit the back-rest to be pivoted with respect to the base portion to a greater extent than the seat portion.

4. A mechanism as claimed in claim 3 in which the locus of movement of the back-rest portion has a smaller radius than that of the locus of movement of the seat portion.

5. A mechanism as claimed in claim 3 in which the base portion comprises a cradle which is rotatably mounted on a pillar.

6. A mechanism as claimed in claim 5 in which the back-rest portion is pivotally connected to the cradle about an axis disposed to the rear of the pillar.

'7. A mechanism as claimed in claim 5 in which the seat portion is pivotally connected to the cradle forwardly of the pillar and is connected by linkage means to the back-rest portion.

References Cited UNITED STATES PATENTS 2,313,559 3/1943 Larsen et al 297302 2,528,223 10/1950 Fox 297301 2,818,911 l/1958 Syak 297303 X 2,956,619 10/1960 Scherer 297303 3,290,091 12/1966 Goodman 297302 BOBBY R. GAY, Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

G. O. FINCH, Assistant Examiner. 

